A method, an apparatus and a system for uplink synchronization are disclosed by the embodiment of the invention. The method includes the following steps: a network equipment configures multi-carrier operation mode for a user equipment and obtains the timing advance TA group message corresponding to each of component carrier CC of the user equipment; the network equipment maintains the TA timer of each TA group according to the TA group information to be uplink synchronized with the user equipment. The embodiment of the invention provides the establishment and maintenance mechanism for uplink synchronization in the case that the timing advance of each component carrier CC is different in the multi-carrier system.